1. Field of the Invention
The present invention relates to a method of preparing silica nanoparticles, by solving a silica constituent from siliceous mudstone, which is amorphous silica mineral resources, into a sodium silicate aqueous solution by a leaching reaction of the siliceous mudstone; preparing a silicate aqueous solution, by removing a sodium constituent by ion exchange; and preparing silica nanoparticles with an average particle dimension being less than 100 nanometers (nm), by flame spray pyrolysis.
2. Description of the Related Art
Generally, a nanoparticle is defined as a particle with the dimension being 100 nm or less. Since nanoparticles have a high specific surface area per weight and novel functionality, these are widely used as advanced materials.
Silica nanoparticles are applicable, in various fields, as the filler for display and semiconductor encapsulants, i.e., epoxy molding compound (EMC), the filler of cosmetics and copy machine toners, the materials for improving the durability of paints and ink and inducing the irregular reflection thereof, and the materials for optical fibers, ceramics and glass industries. The known technologies for preparing silica nanoparticles are disclosed in U.S. Pat. No. 6,322,765B1 (entitled “Process for preparing silicon dioxide” and filed on Sep. 8, 1998), U.S. Pat. No. 6,698,247B2 (entitled “Method and feedstock for making silica by flame combustion” and filed on May 4, 2001), Korean Patent No. 10-0354432 (entitled “Method for forming spherical silica powder by aerosol pyrolysis” and filed on Jul. 12, 2000), and Korean Patent No. 10-0477200 (entitled “Method for manufacturing silica powder using ultrasonic aerosol pyrolysis” and filed on Jun. 5, 2002).
However, most of the relevant patents are focused on only a method of directly preparing silica nanoparticles, using silicon chloride and silicon alkoxide as a reactant. No patent discloses a comprehensive processing technology of preparing silica nanoparticles, by compounding sodium silicate from the siliceous mudstone which is mineral resources containing a silica constituent, preparing the silicate aqueous solution excluding a sodium constituent, and then preparing silica nanoparticles, using the silicate aqueous solution as a reactant.